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Previous studies have highlighted the antitumor effects of mesenchymal stem cellderived extracellular vesicles (MSCEVs), positioning them as a promising therapeutic avenue for cancer treatment. However, some researchers have proposed a bidirectional influence of MSCEVs on tumors, determined by the specific tissue origin of the MSCs and the types of tumors involved. The present study aimed to elucidate the effects of human placenta MSCderived extracellular vesicles (hPMSCEVs) on the malignant behavior of a mouse breast cancer model of 4T1 cells in vitro and in vivo. The findings revealed that hPMSCEVs significantly inhibited the proliferation, migration and colony formation of cultured 4T1 mouse breast cancer cells without inducing apoptosis. Exposure to conditioned medium from 4T1 cells pretreated with hPMSCEVs resulted in decreased angiogenic activity, accompanied by the downregulation of angiogenesispromoting genes in human umbilical vein endothelial cells. In murine xenograft models derived from the 4T1 cell line, local administration of hPMSCEVs substantially hindered tumor growth. Further results revealed that hPMSCEVs inhibited angiogenesis in vivo, as reflected by the use of a vascular growth factor receptor 2Fluc transgenic mouse model. In summary, the results confirmed that hPMSCEVs negatively modulated breast cancer growth by suppressing tumor cell proliferation and migration via an indirect antiangiogenic mechanism. These results underscored the therapeutic potential of EVs, suggesting a promising avenue for alternative anticancer treatments in the future.
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Neoplasias de la Mama , Movimiento Celular , Proliferación Celular , Vesículas Extracelulares , Células Endoteliales de la Vena Umbilical Humana , Células Madre Mesenquimatosas , Neovascularización Patológica , Vesículas Extracelulares/metabolismo , Animales , Células Madre Mesenquimatosas/metabolismo , Células Madre Mesenquimatosas/citología , Femenino , Humanos , Ratones , Neoplasias de la Mama/patología , Neoplasias de la Mama/metabolismo , Neoplasias de la Mama/terapia , Neovascularización Patológica/metabolismo , Línea Celular Tumoral , Células Endoteliales de la Vena Umbilical Humana/metabolismo , Ensayos Antitumor por Modelo de Xenoinjerto , Medios de Cultivo Condicionados/farmacología , Ratones Endogámicos BALB C , Placenta/metabolismo , Placenta/citología , Apoptosis , AngiogénesisRESUMEN
Kuey teow is one of the delicacies of Guangdong, China and is a gluten-free noodle dish made from rice. It has a short storage period and extending the shelf life by quick freezing induces quality deterioration due to temperature fluctuations. To improve its freeze-thaw frozen storage quality, this paper examined the effects of hydroxypropyl corn starch (HCS), guar gum (GG), and compound phosphates (CP) on the quality of quick-frozen kuey teow during freeze-thaw cycles. The mechanism was investigated by identifying changes in the moisture status, aging degree of the starch, and textural and cooking characteristics. The results showed that all three additions improved the toughness, chewiness and steaming characteristics of the kuey teow, with CP significantly enhancing chewiness. XRD and FTIR results revealed that GG more significantly inhibited the decrease of starch crystallinity, while HCS inhibited starch aging. GG, HCS and CP all improved the hydration characteristics and water holding capacity of rice starch. GG enhances the ability of starch to bind more tightly with water, resulting in a more uniform water distribution and a more continuous and tight structure of the kuey teow. This study will provide a theoretical basis for compounding and optimizing the quick-freezing of kuey teow.
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This work investigated the underlying mechanism of thermo-ultrasonic treatment to improve the nutritional properties and emulsion stability of sea bass fish head broth. The effects of ultrasonication on the processing of fish broth were compared with boiling water treatment. The nutritional properties of fish broth mainly include protein, fat, total sugar, 5'-nucleotide and free amino acid content. To achieve a similar effect of nutrient extraction, the thermo-ultrasonic treatment required a shorter time (30 min) than boiling water (120 min). The water-soluble protein, fat and total sugar contents were at their maximum at 120 min of the thermo-ultrasonic treatment. In particular, the fat content increased with the time of thermo-ultrasonic treatment from 0.58% to 2.70%. The emulsion structure of the fish soup was characterized by measuring its color and particle size, using optical microscopy and confocal laser scanning microscopy, and determining its storage stability. Thermo-ultrasonic treatment reduced the particle size of the fish broth emulsion and the fat globules became smaller and more homogeneous. Ultrasonication not only accelerated the nutritional and flavor content of the fish head broth, but also reduced the particle size and enhanced the stability of the emulsified system of the fish broth. The fish head tissue was more severely disrupted by the cavitation effect of an ultrasound, and nutrients migrated more and faster. This was mainly due to the cavitation and mechanical breaking force of the ultrasound on the fish head tissue and the fat globules of the fish broth. Altogether, these findings suggest that the thermo-ultrasonic treatment technique is useful for processing nutrient-rich, storage-stable and ready-to-eat fish head broth.
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Cation ordering in multication perovskites is related to many important material properties and performances, but computational determination of the cation ordering remains a major challenge. Here, we propose a new computational approach by introducing a machine learning recommender system into the basin-hopping framework (RBH) for optimizing cation ordering. Taking the electrocatalyst Ba0.5Sr0.5Co0.8Fe0.2O3 (BSCF5582) as a showcase example, we found that the efficiency of RBH in identifying low-energy configurations outperforms the methods of cluster expansion and conventional basin-hopping. The RBH results revealed that the BSCF5582 catalyst tended to have a layered ordering of A-site cations and disordered B-site cations both in bulk and on the surfaces. Further, on the A-site-terminated surface, we found the segregation of large Ba atoms. Similarly, on the A-site- terminated surface of the recently developed Cs0.2Sr0.8Co0.4Fe0.6O3 (CSCF2846) catalyst, layered ordering at the A-site and surface enrichment of large Cs atoms were also found. The layered ordering was robust against thermal effects, as found from molecular dynamics simulations at 800 K. This work provides a new approach for thermodynamic global optimization of chemical ordering in multicomponent materials.
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BACKGROUND: Current guidelines recommend bismuth-containing quadruple therapy for patients newly diagnosed with Helicobacter pylori (H. pylori) infection. We aimed to compare the efficacy and safety of tetracycline administered three times daily versus four times daily in bismuth-containing quadruple therapy for first-line treatment of H. pylori infection. METHODS: This multicenter, noninferiority, randomized controlled study, conducted in China, recruited treatment-naïve adults with H. pylori infection, randomized 1:1 into two treatment groups to receive either of the following bismuth-containing quadruple therapies: esomeprazole 20 mg twice-daily; bismuth 220 mg twice-daily; amoxicillin 1000 mg twice-daily; and tetracycline 500 mg three times daily (TET-T) versus 500 mg four times daily (TET-F). At least 6 weeks post-treatment, a 13C-urea breath test was performed to evaluate H. pylori eradication. RESULTS: In total, 406 patients were randomly assigned to the two treatment groups. Intention-to-treat eradication rates were 91.63% (186/203; 95% confidence interval [CI] 87.82%-95.44%) versus 90.15% (183/203; 95% CI 86.05%-94.25%) (p = 0.0005) and per-protocol eradication rates were 95.34% (184/193; 95% CI 92.36%-98.31%) versus 95.72% (179/187; 95% CI 92.82%-98.62%) (p = 0.0002) for the TET-T and TET-F group, respectively. TET-T-treated patients had a lower incidence of adverse effects than TET-F-treated patients (21.61% vs. 31.63%, p = 0.024), with no significant differences in compliance to treatment between the groups. CONCLUSION: As a first-line therapy for H. pylori infection, the eradication rate of the TET-T therapy was noninferior to that of the TET-F therapy while significantly reducing the incidence of adverse reactions. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT05431075.
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Antibacterianos , Bismuto , Quimioterapia Combinada , Infecciones por Helicobacter , Helicobacter pylori , Tetraciclina , Humanos , Infecciones por Helicobacter/tratamiento farmacológico , Tetraciclina/uso terapéutico , Tetraciclina/administración & dosificación , Tetraciclina/efectos adversos , Masculino , Persona de Mediana Edad , Femenino , Bismuto/uso terapéutico , Bismuto/efectos adversos , Antibacterianos/uso terapéutico , Antibacterianos/administración & dosificación , Antibacterianos/efectos adversos , Adulto , Helicobacter pylori/efectos de los fármacos , Resultado del Tratamiento , China , Amoxicilina/uso terapéutico , Amoxicilina/administración & dosificación , Esquema de Medicación , Esomeprazol/uso terapéutico , Esomeprazol/administración & dosificación , Anciano , Adulto Joven , Pruebas Respiratorias , Inhibidores de la Bomba de Protones/uso terapéutico , Inhibidores de la Bomba de Protones/administración & dosificación , Inhibidores de la Bomba de Protones/efectos adversosRESUMEN
The reconstruction of the polar CeO2 (100) surface has been a subject of long-standing debates due to its complexity and the limited availability of experimental data. Herein, we successfully reveal a CeO2 (100)-(4 × 6) surface reconstruction by combining in situ spherical aberration-corrected scanning transmission electron microscopy, density functional theory calculations, and a particle swarm optimization-based algorithm for structure searching. We have further elucidated the stabilizing mechanism of the reconstructed structure, which involves the splitting of the filled Ce(4f) states and the mixing of the lower-lying ones with the O(2p) orbitals, as evidenced by the projected density of states. We also reveal that the surface chemisorption properties toward water molecules, an important step in numerous heterogeneous catalytic reactions, are enhanced. These insights into the distinct properties of ceria surface pave the way for performance improvements of ceria in a wide range of applications.
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The chelation reaction of soluble soybean polysaccharide (SSPS) with zinc was investigated. Using response surface methodology, the optimum parameters for SSPS-Zn synthesis were obtained: pH 5.3, SSPS-ZnCl2 mass ratio of 9.44:1, reaction temperature 50.44 °C, and reaction time 1.5 h, with the highest zinc content of 24.73 %. Compared with SSPS, SSPS-Zn increased in rhamnogalacturonan content and decreased in that of neutral monosaccharides (Fuc, Ara, Gal, Glu and Xyl). UV-vis spectra indicated that SSPS-Zn was lower than SSPS in protein content. FTIR spectra indicated that CO group of SSPS was bonded to Zn2+. X-ray diffraction spectra demonstrated that SSPS-Zn had higher crystallinity. Congo red reactions showed that SSPS possessed a triple-helix conformation while SSPS-Zn formed an irregular free-coiled conformation. EDX confirmed SSPS-Zn synthesis successfully. TGA curves exhibited that SSPS-Zn required higher temperature to undergo degradation. AFM revealed that SSPS-Zn was clustered while SSPS was filamentous. SEM micrographs showed the cracked fragments on the surface of SSPS-Zn. By in vitro simulation of gastrointestinal digestion, Zn2+ release reached 68.87 % after 2 h digestion. Consequently, the chelation of SSPS with zinc could change structure and provide a basis for research and application of novel zinc supplements.
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In this study, pectin extracted from pomelo peel was investigated using three different combination methods of pulsed electric field (PEF) and cellulase. Three action sequences were performed, including PEF treatment followed by enzymatic hydrolysis, enzymatic hydrolysis followed by PEF treatment, and enzymatic hydrolysis simultaneously treated by PEF. The three corresponding pectins were namely PEP, EPP and SP. The physiochemical, molecular structural and functional properties of the three pectins were determined. The results showed that PEP had excellent physiochemical properties, with the highest yield (12.08 %), total sugar (80.17 %) and total phenol content (38.20 %). The monosaccharide composition and FT-IR analysis indicated that the three pectins were similar. The molecular weights of PEP, EPP and SP were 51.13, 88.51 and 40.00 kDa, respectively. PEP showed the best gel properties, emulsification stability and antioxidant capacity among the three products, due to its high galacturonic acid and total phenol content, appropriate protein and low molecular weight. The mechanism of PEF-assisted cellulase hydrolysis of pomelo peel was also revealed by SEM analysis. These results suggested that PEF pretreatment was the best method, which not only improved the efficiency of enzymatic extraction, but also reduced resource waste and increased financial benefits.
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Celulasa , Citrus , Peso Molecular , Pectinas , Hidrólisis , Celulasa/metabolismo , Celulasa/química , Pectinas/química , Citrus/química , Antioxidantes/química , Antioxidantes/farmacología , Electricidad , Fenómenos Químicos , Fenoles/química , Frutas/química , Espectroscopía Infrarroja por Transformada de Fourier , Monosacáridos/análisisRESUMEN
To promote the bioconversion of marine chitin waste into value-added products, we expressed a novel pH-stable Micromonospora aurantiaca-derived chitinase, MaChi1, in Escherichia coli and subsequently purified, characterized, and evaluated it for its chitin-converting capacity. Our results indicated that MaChi1 is of the glycoside hydrolase (GH) family 18 with a molecular weight of approximately 57 kDa, consisting of a GH18 catalytic domain and a cellulose-binding domain. We recorded its optimal activity at pH 5.0 and 55 °C. It exhibited excellent stability in a wide pH range of 3.0-10.0. Mg2+ (5 mM), and dithiothreitol (10 mM) significantly promoted MaChi1 activity. MaChi1 exhibited broad substrate specificity and hydrolyzed chitin, chitosan, cellulose, soluble starch, and N-acetyl chitooligosaccharides with polymerization degrees ranging from three to six. Moreover, MaChi1 exhibited an endo-type cleavage pattern, and it could efficiently convert colloidal chitin into N-acetyl-D-glucosamine (GlcNAc) and (GlcNAc)2 with yields of 227.2 and 505.9 mg/g chitin, respectively. Its high chitin-degrading capacity and exceptional pH tolerance makes it a promising tool with potential applications in chitin waste treatment and bioactive oligosaccharide production.
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Quitina , Quitinasas , Micromonospora , Quitinasas/metabolismo , Quitinasas/química , Quitinasas/aislamiento & purificación , Quitinasas/genética , Quitina/análogos & derivados , Quitina/metabolismo , Quitina/química , Concentración de Iones de Hidrógeno , Especificidad por Sustrato , Micromonospora/enzimología , Micromonospora/genética , Hidrólisis , Escherichia coli/genética , Quitosano/química , Estabilidad de EnzimasRESUMEN
A method integrating machine learning with first-principles calculations is employed to forecast the formation energy of delafossite crystals, facilitating the rapid identification of stable crystals. This approach identifies several stable candidates and highlights the importance of atomic ionization energy and electron affinity in the formation of delafossite crystals.
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Saposhnikovia divaricata, 2n = 2x = 16, as a perennial species, is widely distributed in China, Mongolia, Russia, etc. It is a traditional Chinese herb used to treat tetanus, rubella pruritus, rheumatic arthralgia, and other diseases. Here, we assembled a 2.07 Gb and N50 scaffold length of 227.67 Mb high-quality chromosome-level genome of S. divaricata based on the PacBio Sequel II sequencing platform. The total number of genes identified was 42 948, and 42 456 of them were functionally annotated. A total of 85.07% of the genome was composed of repeat sequences, comprised mainly of long terminal repeats (LTRs) which represented 73.7% of the genome sequence. The genome size may have been affected by a recent whole-genome duplication event. Transcriptional and metabolic analyses revealed bolting and non-bolting S. divaricata differed in flavonoids, plant hormones, and some pharmacologically active components. The analysis of its genome, transcriptome, and metabolome helped to provide insights into the evolution of bolting and non-bolting phenotypes in wild and cultivated S. divaricata and lays the basis for genetic improvement of the species.
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Venous thromboembolism (VTE) is a complex disease that can be classified into two subtypes: deep vein thrombosis (DVT) and pulmonary embolism (PE). Previous observational studies have shown associations between lipids and VTE, but causality remains unclear. Hence, by utilizing 241 lipid-related traits as exposures and data from the FinnGen consortium on VTE, DVT, and PE as outcomes, we conducted two-sample Mendelian randomization (MR) analysis to investigate causal relationships between lipids and VTE, DVT and PE. The MR results identified that fatty acid (FA) unsaturation traits (ratio of bis-allylic bonds to double bonds in lipids, and ratio of bis-allylic bonds to total fatty acids in lipids) were associated with VTE (odds ratio [OR]=1.21, 95% confidence interval [CI]: 1.15-1.27; OR=1.21, 95% CI: 1.13-1.30), DVT (OR=1.24, 95% CI: 1.16-1.33; OR= 1.26, 95% CI: 1.16-1.36) and PE (OR=1.18, 95% CI: 1.08-1.29; OR=1.18, 95% CI: 1.09-1.27). Phosphatidylcholines (PC) exhibit potential causal effects on VTE and PE. PC acyl-alkyl C40:4 (PC ae C40:4) was negatively associated with VTE (OR=0.79, 95% CI: 0.73-0.86), while PC diacyl C42:6 (PC aa C42:6) and PC acyl-alkyl C36:4 (PC ae C36:4) were positively associated with PE (OR=1.44, 95% CI: 1.20-1.72; OR=1.22, 95% CI: 1.10-1.35). Additionally, we found that medium LDL had a protective effect on VTE. Our study indicates that higher FA unsaturation may increase the risk of VTE, DVT, and PE. Different types of PC have either promotive or inhibitory effects on VTE and PE, contributing to a better understanding of the risk factors for VTE.
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Análisis de la Aleatorización Mendeliana , Tromboembolia Venosa , Humanos , Tromboembolia Venosa/etiología , Tromboembolia Venosa/epidemiología , Tromboembolia Venosa/sangre , Tromboembolia Venosa/genética , Lípidos/sangre , Factores de Riesgo , Oportunidad Relativa , Embolia Pulmonar/sangre , Embolia Pulmonar/genética , Embolia Pulmonar/etiología , Embolia Pulmonar/epidemiología , FemeninoRESUMEN
BACKGROUND: Bismuth-containing quadruple therapy is the first-line treatment for eradicating Helicobacter pylori (H. pylori). The optimal duration for H. pylori eradication using bismuth-containing quadruple therapy remains controversial. Therefore, we aimed to compare the clinical effects of the 10- and 14-day bismuth-containing quadruple treatment regimen to eradicate H. pylori. METHODS: Treatment-naïve patients with H. pylori infection (n = 1300) were enrolled in this multicenter randomized controlled study across five hospitals in China. They were randomized into 10- or 14-day treatment groups to receive bismuth-containing quadruple therapy as follows: vonoprazan 20 mg twice daily; bismuth 220 mg twice daily; amoxicillin 1000 mg twice daily; and either clarithromycin 500 mg twice daily or tetracycline 500 mg four times daily. At least 6 weeks after treatment, we performed a 13C-urea breath test to evaluate H. pylori eradication. RESULTS: The per-protocol eradication rates were 93.22% (564/605) and 93.74% (569/607) (p < 0.001) and the intention-to-treat eradication rates were 88.62% (576/650) and 89.38% (581/650) (p = 0.007) for the 10- and 14-day regimens, respectively. Incidence of adverse effects was lower in patients who received 10- vs. 14 days of treatment (22.59% vs. 28.50%, p = 0.016). We observed no significant differences in the compliance to treatment or the discontinuation of therapy because of severe adverse effects between the groups. CONCLUSION: Compared with the 14-day bismuth-containing quadruple regimens, the 10-day regimen demonstrated a non-inferior efficacy and lower incidence of adverse effects. Therefore, the 10-day regimen is safe and tolerated and could be recommended for H. pylori eradication (NCT05049902).
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Amoxicilina , Antibacterianos , Bismuto , Claritromicina , Esquema de Medicación , Quimioterapia Combinada , Infecciones por Helicobacter , Helicobacter pylori , Sulfonamidas , Tetraciclina , Humanos , Infecciones por Helicobacter/tratamiento farmacológico , Infecciones por Helicobacter/diagnóstico , Helicobacter pylori/efectos de los fármacos , Persona de Mediana Edad , Masculino , Femenino , Tetraciclina/administración & dosificación , Tetraciclina/uso terapéutico , Antibacterianos/administración & dosificación , Antibacterianos/efectos adversos , Bismuto/administración & dosificación , Bismuto/uso terapéutico , Bismuto/efectos adversos , Adulto , Claritromicina/administración & dosificación , Amoxicilina/administración & dosificación , Sulfonamidas/administración & dosificación , Pirroles/administración & dosificación , Pirroles/efectos adversos , Inhibidores de la Bomba de Protones/administración & dosificación , Inhibidores de la Bomba de Protones/efectos adversos , Pruebas Respiratorias , Resultado del Tratamiento , Anciano , ChinaRESUMEN
Background: Oral immunotherapy (OIT) is a promising allergen-specific approach in the management of food allergy; however, studies on OIT for allergic rhinitis (AR) have rarely been reported. The purpose of this study is to evaluate the efficacy and safety of OIT using enteric-coated capsules for AR induced by house dust mites. Methods: A total of 49 patients with AR were enrolled, including 25 who received subcutaneous immunotherapy (SCIT) and 24 who received OIT. The clinical efficacy and safety in both groups were evaluated. Results: After 1 year of treatment, both SCIT and OIT demonstrated significant therapeutic effects. OIT was found to be more effective than SCIT in reducing the total AR symptom score and improving the results of nasal provocation tests. Local and systemic adverse reactions were observed in the SCIT group, while none were reported in the OIT group. Conclusion: OIT is an effective and safe treatment for mite-induced AR.
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Uncovering mechanisms of endogenous regeneration and repair through resident stem cell activation will allow us to develop specific therapies for injuries and diseases by targeting resident stem cell lineages. Sox9+ stem cells have been reported to play an essential role in acute kidney injury (AKI). However, a complete view of the Sox9+ lineage was not well investigated to accurately elucidate the functional end state and the choice of cell fate during tissue repair after AKI. To identify the mechanisms of fate determination of Sox9+ stem cells, we set up an AKI model with prostaglandin E2 (PGE2) treatment in a Sox9 lineage tracing mouse model. Single-cell RNA sequencing (scRNA-seq) was performed to analyse the transcriptomic profile of the Sox9+ lineage. Our results revealed that PGE2 could activate renal Sox9+ cells and promote the differentiation of Sox9+ cells into renal proximal tubular epithelial cells and inhibit the development of fibrosis. Furthermore, single-cell transcriptome analysis demonstrated that PGE2 could regulate the restoration of lipid metabolism homeostasis in proximal tubular epithelial cells by participating in communication with different cell types. Our results highlight the prospects for the activation of endogenous renal Sox9+ stem cells with PGE2 for the regenerative therapy of AKI.
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Understanding the structures of oxygen vacancies in bulk ceria is crucial as they significantly impact the material's catalytic and electronic properties. The complex interaction between oxygen vacancies and Ce3+ ions presents challenges in characterizing ceria's defect chemistry. We introduced a machine learning-assisted cluster-expansion model to predict the energetics of defective configurations accurately within bulk ceria. This model effectively samples configurational spaces, detailing oxygen vacancy structures across different temperatures and concentrations. At lower temperatures, vacancies tend to cluster, mediated by Ce3+ ions and electrostatic repulsion, while at higher temperatures, they distribute uniformly due to configurational entropy. Our analysis also reveals a correlation between thermodynamic stability and the band gap between occupied O 2p and unoccupied Ce 4f orbitals, with wider band gaps indicating higher stability. This work enhances our understanding of defect chemistry in oxide materials and lays the groundwork for further research into how these structural properties affect ceria's performance.
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Ceria has been extensively utilized in different fields, with surface oxygen vacancies playing a central role. However, versatile oxygen vacancy regulation is still in its infancy. In this work, we propose an effective strategy to manipulate the oxygen vacancy formation energy via transition metal doping by combining first-principles calculations and analytical learning. We elucidate the underlying mechanism driving the formation of oxygen vacancies using combined symbolic regression and data analytics techniques. The results show that the Fermi level of the system and the electronegativity of the dopants are the paramount parameters (features) influencing the formation of oxygen vacancies. These insights not only enhance our understanding of the oxygen vacancy formation mechanism in ceria-based materials to improve their functionality but also potentially lay the groundwork for future strategies in the rational design of other transition metal oxide-based catalysts.
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Chiral epichlorohydrin (ECH) is an attractive intermediate for chiral pharmaceuticals and chemicals preparation. The asymmetric synthesis of chiral ECH using 1,3-dicholoro-2-propanol (1,3-DCP) catalyzed by a haloalcohol dehalogenase (HHDH) was considered as a feasible approach. However, the reverse ring opening reaction caused low optical purity of chiral ECH, thus severely restricts the industrial application of HHDHs. In the present study, a novel selective conformation adjustment strategy was developed with an engineered HheCPS to regulate the kinetic parameters of the forward and reverse reactions, based on site saturation mutation and molecular simulation analysis. The HheCPS mutant E85P was constructed with a markable change in the conformation of (S)-ECH in the substrate pocket and a slight impact on the interaction between 1,3-DCP and the enzyme, which resulted in the kinetic deceleration of the reverse reactions. Compared with HheCPS, the catalytic efficiency (kcat(S)-ECH/Km(S)-ECH) of the reversed reaction dropped to 0.23-fold (from 0.13 to 0.03 mM-1 s-1), while the catalytic efficiency (kcat(1,3-DCP)/Km(1,3-DCP)) of the forward reaction only reduced from 0.83 to 0.71 mM-1 s-1. With 40 mM 1,3-DCP as substrate, HheCPS E85P catalyzed the synthesis of (S)-ECH with the yield up to 55.35% and the e.e. increased from 92.54 to >99%. Our work provided an effective approach for understanding the stereoselective catalytic mechanism as well as the green manufacturing of chiral epoxides.
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Epiclorhidrina , Hidrolasas , Epiclorhidrina/química , Epiclorhidrina/metabolismo , Hidrolasas/genética , Hidrolasas/metabolismo , Hidrolasas/química , Cinética , Estereoisomerismo , Escherichia coli/genética , Escherichia coli/enzimología , Ingeniería de Proteínas/métodos , alfa-Clorhidrina/análogos & derivadosRESUMEN
Electrocatalytic conversion of nitrates and carbon dioxide to urea under ambient conditions shows promise as a potential substitute for traditional urea synthesis processes characterized by high consumption and pollution. In this study, a straightforward one-pot method is employed to prepare a highly efficient FeNC-Fe1N4 electrocatalyst, consisting of atomically dispersed Fe1N4 sites and metallic Fe clusters (FeNC) with particle size of 4-7 nm. The FeNC-Fe1N4 catalyst exhibits remarkable electrocatalytic activity for urea synthesis from nitrate anion (NO3 -) and carbon dioxide (CO2), achieving a urea production rate of 38.2 mmol gcat -1 h-1 at -0.9 V (vs RHE) and a Faradaic efficiency of 66.5% at -0.6 V (vs RHE). Both experimental and theoretical results conclusively demonstrate that metallic Fe clusters and Fe1N4 species provide active sites for the adsorption and activation of NO3 - and CO2, respectively, and the synergistic effect between Fe1N4 and metallic Fe clusters significantly enhances the electrochemical efficiency of urea synthesis. In all, this work contributes to the rational design and comprehensive synthesis of a dual-active site iron-based electrocatalyst, facilitating efficient and sustainable urea synthesis.